Base Reinforcing

The reinforcing is mild steel threaded rod in 6mm . Length was 1m. Get a lot of 6mm nuts and large diamter flat washers with a 6mm hole, you'll see what for in the next pictures.

The reinforcing is now bolted from the underside, with a washer and a nut on the end of each rod holding the steel plate to the plastic base.

Now the nuts have to be run down the threaded bar to hold the washers against the bottom of the plastic base. Bottom being relative to this view. This view is looking at the inside of the plastic pot, the plastic bottom being visible.

From this angle, there is nut, washer, plastic, steel plate, washer, nut going down the threaded bar. You have to put nuts down from this end to keep the steel plate firmly against the plastic. The steel plate is not visible here, it is underneath.

On the other side, the threaded bar has one thread past the nut, as you'll see later.

What I did next was to put ribs along the length of each threaded bar for additional re-inforcement. On a smaller size pot, it is not necessary to have the washers, just thread extra nuts down the bar at various intervals.

The reason for long threaded bar is now apparent. I bend the extra length to take up the space inside the pot, for extra reinforcing.

On a smaller pot, you can use three lengths of mild steel threaded bar cut in half, and get the same effect.